Database links are a critical feature of Oracle that enables users to connect and access data in a remote database from their local database. The Database links feature is particularly useful for individuals – who require access to data that is distributed across multiple databases.
As an essential component of the Oracle database management, it is important to understand the intricacies of creating database links.
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Create Database Links in Oracle
To create a database link in Oracle, users must use the CREATE DATABASE LINK statement, which is similar to a recipe that specifies the necessary ingredients and any special instructions.
To do this, users must provide the connection details and the name of the database link, as well as any options. The basic syntax for creating a database link is as follows:
CREATE DATABASE LINK link_name CONNECT TO username IDENTIFIED BY password USING ‘connect_string’;
Users must specify the name of the database link, the username, and password for the remote database through the CONNECT TO clause.
They must also specify the connection string for the remote database using the USING clause. The connection string comprises the hostname, port, and service name of the remote database.
For Example: Suppose a user wants to create a database link to connect to a remote database called “my_database” with the username “user1” and password “password1.”
In that case, the user would execute the following statement:
CREATE DATABASE LINK remote_link CONNECT TO user1 IDENTIFIED BY password1 USING ‘my_database:port/service_name’;
After creating the database link, the user can access data in the remote database by querying it using SELECT statements or joining it with local tables.
When querying the remote database, it is essential to prefix the table names with the name of the database link. For instance, users can access a table in the remote database named “table_name” using the following query:
SELECT * FROM remote_link.table_name;
Users can also perform other operations, such as inserting, updating, and deleting data in the remote database, provided they have the necessary permissions.
While database links and materialized views can be useful tools for optimizing database performance and accessing data, they differ in how they are used and the scope of their functionality. One key difference is that materialized views store and access data locally, while database links access data in a remote database.
Materialized views can be useful for enhancing the performance of complex queries, while database links can be useful for accessing data in multiple databases or integrating data from various sources.
It is crucial to note that database links are used solely for accessing data in a remote database and not for transferring data between databases. Users must use other tools such as Data Pump or SQL*Loader for this purpose.
Conclusion
Creating a database link is a crucial aspect of managing and optimizing database performance, particularly when dealing with distributed databases.
Understanding how to create and use database links in Oracle can significantly enhance the efficiency and effectiveness of database management.
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